[Qt-interest] [OT] RE: video codecs

[Oliver.Knoll at comit.ch]

Mehmet Kaplan wrote on Friday, June 12, 2009 11:21 AM:

> as i read ffmpeg gives a huge codec support and this support is
> growing. but it can't automatically detect the codec installed on the
> system.  
> basicly really i want is a phonon like system  which detects the
> codec installed, plus gives frame data for further process (not
> available in phonon), also.  

What do you mean by THE codec? There is no such thing as THE codec on a system. Usually there are SEVERAL codecs available, such as MJPEG, h.264, MPEG 2 etc., and usually they are somehow "known" to the media system, for example as DirectShow filters. So when you try to play a given media stream the applicable codecs are detected and used for decoding that stream. Likewise if you want to ENCODE data you have to specify WHICH of the (possibly many) codecs you want to choose.

And AFAIK this is exactly what ffmpeg does: it provides you a bunch of codecs, and possibly even can make use of the codecs which are installed on the system and are available as DirectShow filters (not sure about that though, read the ffmpeg docs).

So if you mean by "[ffmpeg] can't automatically detect the codec installed on the system" that "ffmpeg can't use already installed codecs (which are available as DirectShow filters)", and the ffmpeg docs state explicitly that, then yes, you would need another solution, probably a solution directly based on DirectShow (read: platform dependent).

On the other hand, what is the use case that you explicitly want to use "exactly this codec which is installed on the system"? Typically a use-case scenario for me would be "I want to encode the data as h.264 in a platform-independent way", and if ffmpeg provides such a codec (whether it brings its own plugins or makes use of existing DirectShow ones I don't care) then I would be happy.

But maybe I don't understand your actual question?

Oh, and by the way, I just found this one: http://ffmpeg.org/faq.html#SEC29 - "If you have built FFmpeg with ./configure --enable-avisynth (only possible on MinGW/Cygwin platforms), then you may use any file that DirectShow can read as input."


Cheers, Oliver
-- 
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22